Front and side-loading machines require a separate bobbin case which also acts to control the bobbin tension. Although not generally recommended, more advanced sewists like to adjust the lower tension to accommodate special threads, such as when using a handwound bobbin of thicker decorative thread. You can avoid tricky tension adjustments afterwards by having an extra bobbin case on hand specially adjusted for thicker or thinner threads.

JANOME (Manufacturer) -> Spare parts (Accessory type) -> For sewing machines (Function) -> Vertical, 5 mm (Hook type)